Plastic lenses are lightweight, less fragile, and dyeable, as compared with inorganic lenses. For these reasons, plastic lenses for use in eyeglasses and sunglasses have become widespread. A variety of resins have heretofore been developed and used. Representative examples among them include allyl resins obtained from diethylene glycol bis-allyl carbonates and diallyl isophthalates, and (meth)acrylic resins obtained from (meth)acrylates. Examples of higher refractive index resins include thiourethane resins obtained from isocyanates and thiols (Patent Document 1).
Owing to changes in lifestyle, the population of people enjoying physical activities such as sports while wearing sunglasses has recently been increased. In addition, due to growing safety awareness, children's eyeglasses have been increasingly demanded to be hardly cracked. From these circumstances, there has been an increasing demand for a base material having a lighter weight and a good impact resistance. In response to these growing requirements, a urethane urea molded product as a base material having good impact resistance has been developed for eyeglass lenses (Patent Documents 2 to 6).